In this paper we analyse the characteristics of 2sg verb-final -tu in Sicilian. Although this is generally referred to as an enclitic subject pronoun, it is clear that it is different from the subject clitics found in northern Italian dialects. The question of whether it is an actual subject enclitic or rather an inflectional affix remains controversial. The primary empirical goal of this study is to provide a general characterization of the synchronic properties of this element, focusing firstly on its grammatical status, and secondly on the distributional differences with respect to the 2pl ending -vu. This comparison will lead us to the conclusion that -tu and -vu instantiate a path of grammaticalization, and that their origins are to be sought in the morphosyntactic reflexes of the feature ‘hearer’. More specifically, we claim that the original subject pronoun was at some stage the phonological realization of the head of the functional projection HearerP, but has been subsequently reanalysed as a bound morpheme encoding agreement. This diachronic account straightforwardly explains the flows and problems with the historical analysis that assumes disambiguation in the verbal paradigm to be the triggering factor.